GB2047980A

GB2047980A - Submerged fuel pumps

Info

Publication number: GB2047980A
Application number: GB8013725A
Authority: GB
Original assignee: Mitsuba Electric Manufacturing Co Ltd
Current assignee: Mitsuba Corp
Priority date: 1979-04-26
Filing date: 1980-04-25
Publication date: 1980-12-03
Also published as: DE3016086C2; GB2047980B; DE3016086A1

Abstract

A fuel pump is provided in a fuel supplying system of a vehicle such as an automobile. The electric motor for driving the pump is completely immersed in the flow of fuel for cooling, thereby attaining an extended service life. The brush lead (8) of such a motor-immersed fuel pump is coated with or composed of a material which is non-reactive with the fuel, e.g. the lead may be copper coated with nickel, tin, silver, silver alloy or aluminium. <IMAGE>

Description

SPECIFICATION Submerged fuel pumps The present invention relates to a fuel pump whose drive motor is immersed in the flow of fuel being pumped for the purpose of cooling the motor.

Since the motor is completely immersed in the flow of fuel, heat generated inside the motor is carried away and the motor can be maintained at low temperatures as desired. Moreover, sparks between the motor commutator and the brush co operating with the commutator are suppressed and the induced explosion of vapourized fuel by these sparks is prevented from occurring. These are the main advantages of a motor-immersed fuel pump. A lead wire must be provided for the electrical connection between the brush and an exterior source (not shown). It is a well established practice to use copper or copper alloy as the most suitable material for the lead wire for various reasons, such as high electrical conductivity, excellent mechanical workability, and economical advantage.If a fuel pump is of the type in which the motor is not immersed in the flow of fuel, but rather positioned in the atmosphere, no particular problems with respect to the lead wire exist.

However, in the case of a motor-immersed fuel pump, there are disadvantages since the copper or copper alloy brush lead wire is also immersed in the fuel, usually petrol. In this instance, the copper ingredients in the lead wire react with petrol so that the petrol is adversely effected such as being oxidized, and thus oxidized petrol promotes the corrosion of the lead wire. Such phenomenon of the deterioration of fuel, usually petrol, by reaction with copper ingredients, particularly copper ions, is well known.

When use is made of alcohol enriched petrol, so-called gasohol, which has recently become very popular as a means to curb energy shortage problems, the reaction rate between the fuel and the copper ingredients increases markedly and there is even a possibility that the lead wire including copper as an ingredient could be partly eaten away due to extensive corrosion after short hours of service. Moreover, in order to obtain required flexibility, the lead wire is usually made by twisting or weaving a plurality of fine strand wires, rather than a single thick wire, which makes the contact area with fuel larger; therefore, the reaction rate is increased and the lead wire is easier to corrode.

It is thus an object of the present invention to provide, in a motor-immersed fuel pump, a brush lead structure which avoids fuel, usually petrol, from becoming deteriorated.

It is another object of the present invention to provide, in a motor-immersed fuel pump, a brush lead structure which avoids the brush lead being corroded by fuel, usually petrol.

The present invention resides in a fuel pump of the kind in which a motor for driving the pump is completely immersed in the flow of fuel, in which at least that part of a lead wire, one end of which is connected to a brush which is in sliding contact with a commutator of said motor, exposed to said fuel, is composed of a material non-reactive with said fuel.

The present invention will be further described by way of example, with reference to the drawings, in which: Fig. 1 is a partially cut-away cross-sectional view of a motor-immersed fuel pump; Fig. 2 is a larger scale perspective view showing the brush and lead wire assembly for the fuel pumps, and Fig. 3 is a cross-sectional view of a fine strand of the brush lead wire.

As schematically shown in Fig. 1, a motorimmersed fuel pump is a kind of fuel pump used in an engine-driven vehicle such as automobiles.

Referring to Fig. 1, a motor-immersed fuel pump 1 includes a pump mechanism 2, which is of the vane type. The vane pump 2 includes a rotor 2a which is fixedly mounted on and at one end of a driving shaft 3a of an electric motor 3. The motor 3 is completely housed in a casing 5 and a motor chamber 4 is defined therebetween. Thus, when the pump rotor 2a is rotated by the motor 3, fuel is introduced into the motor chamber 4 through an inlet port 1 a and discharged exteriorly through an outlet port 1 b, as shown by the arrows.

Referring to Fig. 2, there is shown a brush lead wire 8 of the-pump. One end of the lead wire of is connected to a brush 7 which is normally in contact with a commutator 6 (Fig. 1) for operation. Although the lead wire 8 shown in Fig.

2 is formed by twisting a plurality of fine strand wires 9 together, it should be obvious that the lead wire can be formed by weaving or braiding a plurality of fine strand wires or by a single thick wire.

In accordance with one embodiment of the present invention, the lead wire 8 is formed by a material which is non-reactive with fuel, particularly petrol, and does not contain copper ingredients. Some examples of such material include tin, nickel, silver, silver alloy, stainless steel, and aluminium. Where the lead wire is formed by one of these materials, the lead wire will not have adverse effects on the fuel and also the lead wire is virtually free of corrosion.

However, it is still preferable to use copper or copper alloy to form. the lead wire 8 from over-all considerations including electrical conductivity, mechanical workability, and economical advantage.

Therefore, as another embodiment of the present invention, the lead wire is formed by copper or copper alloy core region and a protective layer completely surrounding the core region. Such a protective layer can be formed on a fine wire strand or directly on a lead wire.

Referring to Fig. 3, there is shown a fine wire strand 9 which comprises a copper or copper alloy core region 11 and a protective layer 12 completely surrounding the core region 11. The protective layer 12 is formed by a material which does not contain copper ingredients and is highly non-reactive with fuel, particularly petrol. The protective layer 12 may be formed by spraying, electro-plating, or any other convenient techniques. Preferred materials for the protective layer 12 includes tin, nickel, silver, silver alloy, and aluminium.

As described above, the lead wire 8 of the fuel pump has a structure in which at least a part exposed to fuel is composed of a material which is highly non-reactive with the fuel; therefore, the fuel receives no adverse effects from the lead wire and vice versa. This also enables to supply fuel of the guaranteed quality to an internal combustion engine at all times, which, in turn, contributes to the maintenance of a high, proper combustion efficiency and to the protection of the engine itself. On the other hand, since the lead wire is virtually free of corrosion, the pump can be used for an extended period of time. According to the prior art, when the lead wire became disconnected due to corrosion, the fuel pump as a whole had to be replaced, or at least dismantled for repairment, while the present invention does not possess such disadvantage.

As shown in Fig. 2, the connection between the lead wire 8 and the brush 7 is generally formed by planting one end of lead wire 8 in the brush 7 when the brush 7 is manufactured mainly from carbon by sintering. However, since the temperature is raised to about 800 degrees C during such sintering process, the lead wire 8 must be composed of materials which are resistant to such a high temperature condition if the connection between the brush and the lead wire is to be formed at the time of sintering the brush 7.

In accordance with one embodiment of the present invention, use was made of a lead wire 8 formed by a plurality of fine wire strands 9, each comprising a copper core region 11 and a nickel electro-plated layer 12 of 2 to 6 microns thick on the peripheral surface of the copper core region 11. One end of this lead wire 8 was planted in the brush 7 and the brush was sintered at about 800 degrees C, thereby forming the connection between the lead wire 8 and the brush 7 simultaneously. It was found that the nickel electro-plated layer 12 of this thickness range was not destroyed; and, therefore, the copper core region 11 was not exposed as a result of subjecting to such a high temperature condition. It was also found that the above-noted thickness range of the nickel electro-plated layer 12 did not impair the flexibility required for the lead wire 8.

An upper limit for the thickness of the nickel electro-plated layer 12 should be determined in such a manner that the lead wire 8 as a final product still has enough flexibility as required. On the other hand, the nickel electro-plated layer 1 2 must be thick enough to protect the copper core region 1 The preferred thickness range was found to be 2 to 6 microns for nickel. This embodiment is particularly advantageous because copper and nickel are less expensive. It is also advantageous because the prior art sintering technique can be applied to form the connection between the lead wire 8 and the brush 7.

it will be understood that various changes in details, materials, and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made within the scope of the invention.

However, while the invention has been described with reference to the structure disclosed herein, it is not to be confined to the details set forth, and the invention includes such modifications or changes as may come within the scope of the

Claims

claims. CLAIMS

1. A fuel pump of the kind in which a motor for driving the pump is completley immersed in the flow of fuel, in which at least that part of a lead wire, one end of which is connected to a brush which is in sliding contact with a commutator of said motor, exposed to said fuel, is composed of a material non-reactive with said fuel.

2. A fuel pump as claimed in claim 1 wherein said lead wire is formed by twisting or weaving a plurality of fine strand wires.

3. A fuel pump as claimed in claim 1 or 2 wherein saidlead wire comprises a copper or copper alloy core region and a protective layer formed on said core region the protective layer being of a material non-reactive with said fuel.

4. A fuel pump as claimed in claim 3 wherein said protective layer is a nickel electro-plate.

5. A fuel pump as claimed in claim 4 wherein the thickness of said nickel electro-plated layer is in the range of 2 to 6 microns.

6. A fuel pump as claimed in any preceding claim wherein said fuel is petrol.

7. A fuel pump as claimed in claim 6 wherein alcohol is added to said petrol.

8. A fuel pump constructed substantially as herein described with reference to and as illustrated in the drawings.